資料來源 : Webster's Revised Unabridged Dictionary (1913)
5. (Mus.) Necessary; indispensable; -- said of those tones
which constitute a chord, in distinction from ornamental
or passing tones.
6. (Med.) Idiopathic; independent of other diseases.
{Essential character} (Biol.), the prominent characteristics
which serve to distinguish one genus, species, etc., from
another.
{Essential disease}, {Essential fever} (Med.), one that is
not dependent on another.
{Essential oils} (Chem.), a class of volatile oils, extracted
from plants, fruits, or flowers, having each its
characteristic odor, and hot burning taste. They are used
in essences, perfumery, etc., and include many varieties
of compounds; as {lemon oil} is a terpene, {oil of bitter
almonds} an aldehyde, {oil of wintergreen} an ethereal
salt, etc.; -- called also {volatile oils} in distinction
from the fixed or nonvolatile.
資料來源 : WordNet®
lemon oil
n : fragrant yellow oil obtained from the lemon peel